MIXING AND CRYSTALLIZATION Editorial board: A.W. Nienow, Birmingham, United Kingdom K. Ogawa, Tokyo, Japan S. Rohani, Saskatchewan, Canada L.T. Fan, Kansas, U.S.A. J.J. Chen, Auckland, Australia Mixing and Crystallization Selected papers from the International Conference on Mixing and Crystallization held at Tioman Island, Malaysia in April 1998 Edited by Baskar Sen Gupta and Shaliza Ibrahim Institute of Post Graduate Studies and Research. University of Malaya. Kuala Lumpur; Malaysia The conference was organised by: Institute of Post Graduate Studies and Research, University of Malaya, Kuala Lumpur, Malaysia and Special Research Centre for Multiphase Processes, University of Newcastle, Callaghan, Australia The conference was co-sponsored by: The Institute of Chemical Engineers, United Kingdom The Institution of Engineers, Malaysia SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. A C.I.P. Catalogue record for this book is available from the Library of Congress. ISBN 978-90-481-5410-4 ISBN 978-94-017-2290-2 (eBook) DOI 10.1007/978-94-017-2290-2 Printed on acid-free paper AII Rights Reserved © 2000 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 2000 Softcover reprint ofthe hardcover Ist edition 2000 No part of the material protected by this copyright notice may be reproduced Of utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner. To Mohd. Ali Hashim Professor ofC hemical Engineering, University ofM alaya, and NafisAhmed Department ofC hemical Engineering, University ofN ewcastle, Australia for their inspiration and support. Contents Foreword xi MIXING G.D. Rigby, G. Lane, G.M. Evans CFD Modelling of Hydrodynamic Conditions within the Wake of Mixing Impeller Blades 1 M.Liu, C.D. Andreasen, R. La Roche, S. Choudhary Visualisation and quantification of laminar flow mixing in a stirred tank reactor 15 K.C. Lee, N.A. Borret, M. Yianneskis Turbulence structure and isotrophy in stirred vessels 29 Z.D. Chen, J.J.J. Chen A study of agitated gas-liquid reactors with concave blade impellers 43 W. Bujalski, D. Hari-Prajitno, K. Takenaka, J. McKemmie, A.W.Nienow Studies of aerated mixing with multiple axial flow hydrofoil (APV-B2) impellers 57 M.S. Takriff, W.R. Penney, J.B. Fasano Interstage backmixing of a gas-liquid multistage, mechanically-agita- ted, compartmented column 67 G.M. Evans, W.P. Mao, G.J. Jameson Mass transfer in a plunging liquid jet 75 G.R. Drewer, N. Ahmed, G.J. Jameson An optimum concentration for the suspension of solids in stirred vessels 83 CRYSTALLIZATION Y. Yamazaki, H. Yazawa, Y. Hirata Freeze concentration with ice-lining in a crystallizer of agitated vessel 95 viii H. Schubert, A. Mersmann How agglomeration Processes affect experimentally determined nucleation rates 105 R.A. Williams, X. Jia, R.M. West, K.J. Roberts On-line measurement of solids distribution I stirred tanks and crystallizers using electrical computed tomography 113 K. Ogawa, Z. Sha, S. Palosaari A new expression for dispersedness of multi-phase taking account of consideration of local size distribution 125 Z. Sha, S. Palosaari Size dependent classification function in imperfectly mixed suspen- sion continuous crystallizer 133 M.L.J. van Leeuwen, D.S.L. Bruinsma, G.M. van Rosmalen, M.J. Hounslow, M.M. Seckler An experimental study to the effects of supersaturation ratio, impeller design and Impeller speed on agglomeration of aluminium trihydroxide 151 R.M. Cooper, G.M. Parkinson, O.M.G. Newman The precipitation of silica from acidic zinc leach liquors 163 V. Nallet, D. Mangin, J.P. Klein Precipitation of microcrystals of salicycle acid in a T mixer: experimental study and Modelling 177 N.S. Tavare Mixing, reaction and precipitation: The Barium Sulphate Precipitation System 191 R. Philips, S. Rohani, J. Baldyga Micromixing in a Single Feed Semibatch Precipitation Process 205 A. Futia, H.M. Ang, D. Ilievski Yield Model of a Batch Gibbsite Precipitator 215 T.S. Li, A.L. Rohl, D. Ilievski Modelling of a Constant Supersaturation Precipitator 227 IX A. Mersmann, C. Heyer, H. Schubert How to Influence the Median Crystal Size of Precipitates 243 L.T. Fan, S.T. Chou, W.Y. Chen, M. Bai, J.P. Hsu Modeling Fluctuation in the Growth Rate of a Single Crystal 253 A.M. Neumann, S.K. Bermingham, H.J.M. Kramer, G.M. van Rosmalen Modeling the Attrition Process in a 22 Liter Draft Tube Crystallizer 267 M.L.J. van Leeuwen, D.S.L. Bruinsma, G.M. van Rosmalen Computational Fluid Dynamics Approach to Precipitation Reactions: The Importance Of Subgrid-Scale Fluctations 281 J.G. Wijers, J.H.A. Schoenmakers, D. Thoenes Scaling-up of Reactive Crystallizers 293 T. Nomura, K. Shimizu, K. Takahashi In-situ Measurement Method of Crystal Concentration in a Seeded Batch Crystallizer 309 K.C. Lim, M.A. Hashim, B. Sen Gupta Monte Carlo Simulation of the Crystal Size Distribution with Attrition Effects in a Mixed Suspension Crystallizer 317 E.T. White A Review of the Crystallization of Sugar 329 FOREWORD We are honoured to present this collection of selected papers from the International Conference on Mixing and Crystallization, held at the Tioman Island, Malaysia in April, 1998. We are grateful to the editorial board comprising five eminent researchers in the field of mixing and crystallization for their thoughtful review and suggestions. In order to make this book as current as possible some of the papers have been thoroughly revised, which caused some delay in bringing out this edited version. We received necessary support from the Institute of Post Graduate Studies and Research, the University of Malaya and the Special Research Centre for Multiphase Processes, and the University of Newcastle, Australia in organizing this conference. We are indebted to the Institute of Chemical Engineers, United Kingdom, and the Institution of Engineers, Malaysia for their sponsorship. We would like to thank K.C. Lim, Dr. C. Ramakanth and Ms. Zubaidah for their help at the various stages of editing. We would also like to express our gratitude to Professor Mohd. Ali Hashim and Dr. Nafis Ahmed for their help and encouragement. Finally, I would like to thank Kluwer Academic Publishers for publishing this book. Bhaskar Sen Gupta Shaliza Ibrahim University of Malaya, Kuala Lumpur xi CFD MODELLING OF HYDRODYNAMIC CONDITIONS WITHIN THE WAKE OF MIXING IMPELLER BLADES G.D. RIGByl., G. LANE1. AND G.M. EVANSl. Research Centre for Multiphase Processes, Department of I. Chemical Engineering, The University ofN ewcastle, Callaghan, NSW 2038, Australia CSIRO Division ofM inerals 2. P.D. Box 312, Clayton South, Victoria 3169, Australia Abstract Computational fluid dynamics simulations have been used to simulate the flow field within the impeller swept region of a baffled stirred tank. Rushton turbine and flat paddle impeller configurations are investigated using sliding mesh techniques, for which no experimental input is necessary. The results from the CFD simulations show reasonable agreement with experimental data for the location of important flow structures close to the impeller blades, including the position of flow recirculation and axis of trailing vortex pairs generated within the wake at the rear of each blade, and the angle-resolved periodicity of the flow field between successive impeller blades. 1. Introduction 1.1. BACKGROUND The use of mechanical impeller systems for the agitation or mixing of fluids is an important unit operation in many chemical process industries. As a result, experimental studies of the fluid flow within the bulk region of impeller stirred reaction vessels have been reported in great detail in literature (e.g. Ranade and Joshi, 1990a; Jaworski et ai., 1991; Luo et ai., 1993; Jaworski et ai., 1996). This is particularly the case for the configuration of a disc turbine, which has probably been the most widely studied configuration, and has been essentially established as a reference configuration both within research organisations and the mixing industry. There have been fewer studies of the hydrodynamic conditions within the impeller swept region of stirred tank systems. This region is of significance in B. Sen Gupta and S. Ibrahim (eds.), Mixing and Crystallization, 1-13. © 2000 Kluwer Academic Publishers.